An unmanned aerial vehicle (UAV) is a remotely piloted or self-piloted aircraft that can carry cameras, sensors, communications equipment, and/or other payloads. UAVs have been used in a reconnaissance and intelligence-gathering role since the 1950s. Today, UAVs are used for additional purposes, such as target acquisition and/or designation, data acquisition, communications relay, decoy, jamming, harassment, ordinance delivery, and supply flights. This increased role of the UAVs has lead to many advancements in UAV design.
A UAV is generally designed to be recoverable and reusable for multiple missions. There are many UAV designs, including fixed-wing type configurations, helicopter type configurations, and ducted type configurations. Each of these designs has a limited range. Typically, a UAV having a fixed-wing type configuration can travel further than a UAV with either a helicopter type or a ducted type configuration. However, regardless of the design, the UAV stops flying when the aircraft runs out of fuel.
As the role of the UAV increases, it would be beneficial to increase the range and loiter time of the UAV. One way to increase the mission duration of the UAV is to allow the UAV to refuel during a mission. Aerial refueling of military aircraft, such as jet fighters and helicopters, has been done for years. Typically, a tanker aircraft carrying fuel extends a flying boom or probe beneath the tanker aircraft. A pilot maneuvers the receiving aircraft beneath the probe, connecting the probe to a receptacle on the exterior of the receiving aircraft. The tanker aircraft supplies fuel to the receiving aircraft once the probe is coupled to the receiving aircraft.
Currently, UAV's do not have the ability to conduct mid-air refueling. Unlike a manned aircraft, the UAV does not have a pilot that can maneuver the aircraft into position relative to the tanker aircraft and maintain the relative position during refueling. The UAV lacks relative navigation capabilities, which would guide the UAV to a tanker aircraft. Relative navigation refers to providing a navigation solution that takes into account the relative location of two moving objects. It is much easier to navigate a moving object to a fixed position, such as landing an aircraft on a runway. Because both the UAV and the tanker aircraft are moving with respect to the earth during mid-air refueling, the navigation solution is much more complex.
Thus, it would be beneficial to provide the UAV with highly reliable relative navigation capabilities with a high degree of confidence that would allow the UAV to safely and efficiently rendezvous with the tanker aircraft for aerial refueling. As a result, the UAV may be used on longer and/or more complex missions.